fix: corrigir memory leaks e testes de mocks

- Fechar ConvexClient antigo antes de criar novo (evita memory leak)
- Adicionar flag disposed para prevenir race condition em useEffect
- Reduzir polling SSE de 1s para 5s (balanco entre responsividade e carga)
- Adicionar .take() aos mocks de testes para compatibilidade

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

tests/machines.getById.test.ts

@@ -60,8 +60,12 @@ describe("convex.machines.getById", () => {
           collect: vi.fn(async () => [
             { revoked: false, expiresAt: FIXED_NOW + 60_000, lastUsedAt: FIXED_NOW - 1000, usageCount: 5 },
           ]),
+          take: vi.fn(async () => [
+            { revoked: false, expiresAt: FIXED_NOW + 60_000, lastUsedAt: FIXED_NOW - 1000, usageCount: 5 },
+          ]),
         })),
         collect: vi.fn(async () => []),
+        take: vi.fn(async () => []),
       })),
     }